Video preview

js

$(function() {
  $('#video__play').on('click', function(e) {
    let dataYoutube = $(this).closest('.video').data('youtube');
    $(this).replaceWith('<div class="embed-responsive embed-responsive-16by9"><iframe class="embed-responsive-item" src="https://www.youtube.com/embed/' + dataYoutube + '?autoplay=1" frameborder="0" allowfullscreen></iframe></div>');
    e.preventDefault();
  });
});

pug

.video(data-youtube='8z9kooDFTSE')
  a#video__play.video__play(href='#')
    img.img-responsive.video__img(src='img/video.jpg', alt='Трейлер')/

Video preview

<div class="video" data-youtube="8z9kooDFTSE">
  <a class="video__play" id="video__play" href="#">
    <img class="img-responsive video__img" src="img/video.jpg" alt="Трейлер">
  </a>
</div>